In less than a year, young Prince George will have to follow a long-standing royal tradition. Today, July 22, he celebrates his 11th birthday. His mother, Kate Middleton, has shared a heartfelt black-and-white photo of George in a suit on Instagram, wishing him a very happy birthday.

This is quite different from the typical colorful pictures we usually see of George and his siblings, Princess Charlotte and Prince Louis. George’s birthday comes after a busy time of travels and events. He’s had the chance to attend exciting occasions like the men’s Euro 2024 final in Berlin and Taylor Swift’s concert at Wembley Stadium with his father, Prince William.

But next year, things might change drastically. When George turns 12, a royal rule that’s been around for years could take effect. This rule, meant to ensure the safety of the royal lineage, may prevent George from traveling with his father.

According to this rule, once George turns 12 in July 2025, he might have to travel separately from Prince William to avoid any potential disaster affecting both. This isn’t new. King Charles III’s former pilot, Graham Laurie, has talked about how similar rules applied to Prince William when he reached the age of 12 back in 1994.

Laurie explained that until that age, the entire family—Prince Charles, Princess Diana, William, and Harry—could fly together. But once William turned 12, separate flights were mandatory unless they had Her Majesty’s written permission.

So far, it’s unclear if this rule will be enforced for Prince George. Heirs to the throne typically need the monarch’s permission to travel together. This was the case in 2014 when Prince William and Kate flew to Australia with their children. The royal press office mentioned to BBC’s Newsround that the Queen had granted permission for this trip, indicating that the final decision lies with the reigning monarch.